A gas boiler may be classified into a condensing gas boiler and a non-condensing gas boiler depending on whether or not absorbing condensation latent heat of combustion gas generated in a burner therein.
The condensing gas boiler is a boiler collecting condensation latent heat of water vapor contained in combustion gas, and is provided with a separate latent-heat exchange unit for collecting latent heat.
FIG. 1 is a diagram illustrating a downstream type condensing gas boiler among conventional condensing gas boilers. As shown in FIG. 1, the conventional condensing gas boiler is configured with an expansion tank 3 storing heating water that flows in through a circulating heating water inflow pipe 1, a circulating pump 4 circulating the heating water discharged through a circulating heating water discharge pipe 2 connected to the expansion tank 3, a latent-heat exchange unit 5 exchanging heat of the heating water being pressure delivered by the circulating pump 4, a sensible-heat exchange unit 6 transferring heat energy of a burner 7 to the heating water that is primarily preheated through the latent-heat exchange unit 5, a three way valve 10 supplying the heating water to a heating water supply pipe 8 when performing a heating operation and to a hot water supply heat exchange unit 9 when performing a hot water supply operation, and the hot water supply heat exchange unit 9 heating direct water to supply hot water to a user when performing the hot water supply operation.
An operation process of the conventional condensing gas boiler shown in FIG. 1 will be described.
When an indoor space is heated, heating water of which heat is transferred to a heating required zone flows in the expansion tank 3 via the circulating heating water inflow pipe 1, and the heating water discharged from the expansion tank 3 to the circulating heating water discharge pipe 2 is supplied to the latent-heat exchange unit 5 via the circulating pump 4 to exchange heat with combustion gas while passing a heat exchange pipe 5a installed at the latent-heat exchange unit 5 such that temperature of the heating water is primarily raised. At this point, condensed water being generated is discharged to an outside through a condensed water outlet 13.
Also, the heating water of which the temperature is raised in the latent-heat exchange unit 5 secondarily exchanges heat with the combustion gas through the sensible-heat exchange unit 6 to raise the temperature of the heating water, and then is supplied to a heating required zone through the heating water supply pipe 8 via the three way valve 10.
In a hot water supply operation, heating water being heated while sequentially passing the latent-heat exchange unit 5 and the sensible-heat exchange unit 6 is supplied to the hot water supply heat exchange unit 9 via the three way valve 10 to exchange heat with direct water that flows in through a direct water inlet pipe 11, and the direct water becomes hot water to be discharged through a hot water supply pipe 12 and to be supplied to the user.
The above described conventional condensing gas boiler is disclosed in Registered Korean Patent No. 10-0976032.
The above described conventional condensing gas boiler, however, heats direct water using the hot water supply heat exchange unit 9 to produce hot water such that it has problems in that a heating of the direct water is a time-consuming process and also thermal efficiency is degraded.
In addition, because the sensible-heat exchange unit 6 and the latent-heat exchange unit 5 are respectively manufactured using a separate heat exchange pipe, there are problems in that a manufacturing cost is high and a manufacturing process is complicated.